An ink-jet printer has many advantages, such as high-speed printing capability, very low noise during printing, flexibility of ink, and availability of inexpensive plain paper. In recent years, an ink-on-demand ink-jet printer, which discharges ink droplets only when printing is required, is the mainstream among ink-jet printers. This ink-on-demand ink-jet printer has advantages, for example, in that it eliminates the need for collecting unused ink droplets.
The ink-on-demand ink-jet printer includes an electrostatic driving ink-jet printer, which utilizes electrostatic force as driving means in the method for discharging ink droplets, a piezoelectric driving ink-jet printer, which utilizes a piezoelectric element as driving means, and a Bubble Jet® ink-jet printer, which utilizes a heating element.
In the electrostatic driving ink-jet printer, a diaphragm and an individual electrode disposed opposite to the diaphragm are electrically charged and thereby the diaphragm is attracted and bends toward the individual electrode. Such a mechanism by which two substances are electrically charged for driving in a small apparatus is generally referred to as an electrostatic actuator. In an apparatus using an electrostatic actuator, such as an ink-jet printer, an insulating film for preventing dielectric breakdown and short is generally formed between two electrically charged substances (a diaphragm and a individual electrode).
In a conventional electrostatic actuator and a method for manufacturing the conventional electrostatic actuator, an individual electrode for driving a diaphragm is formed in a staircase pattern, and an insulating film for preventing dielectric breakdown and short is formed on the individual electrode. Silicon oxide or silicon nitride is used as a material for the insulating film (see, for example, Patent Document 1).
Furthermore, in a method for manufacturing a conventional semiconductor device, a gate insulating film of a field-effect transistor is also formed of silicon oxynitride, as well as silicon oxide or silicon nitride, formed by plasma chemical vapor deposition (CVD) (see, for example, Patent Documents 2 and 3).
[Patent Document 1] JP-A-1-2000-318155 (p. 2, FIG. 2).
[Patent Document 2] JP-A-1-2004-153037 (p. 2).
[Patent Document 3] JP-A-1-2003-142579 (p. 2).